Heart disease is one of the leading causes of death. Currently, medical science cannot reverse the damage done to the cardiac muscle by heart disease. The only known solution is a heart transplant. However, the number of cardiac patients in need of a heart transplant far exceeds the limited supply of donor hearts available.
The scarcity of human hearts available for transplant, as well as the logistics necessary to undertake heart transplant surgery, make a permanently implantable cardiac assist device a viable option for many heart patients. An aortic blood pump can be permanently surgically implanted in the wall of the aorta to augment the pumping action of the heart. The aortic blood pump is sometimes referred to as a mechanical auxiliary ventricle assist device, dynamic aortic patch, or permanent balloon pump.
Typically, the aortic blood pump includes a membrane that moves relative to a pump body as the body internal pressure is cycled in a predetermined synchronous pattern with respect to the diastole and systole of the patient to elevate aortic blood pressure immediately after aortic valve closure. Membrane movement can be accomplished by means of an external supply tube connected to the bladder or an implanted supply reservoir. Electrical leads from electrodes implanted in the myocardium are likewise brought out through the skin by means of the PAD. The “R” wave of the electrocardiograph can be employed to control the fluid pressure source to inflate and deflate the inflatable chamber in a predetermined synchronous relationship with the heart action.
The aortic blood pump acts to assist or augment the function of the left ventricle and is typically restricted to use in patients who have some functioning myocardium. The aortic blood pump does not need to be operated full time, and in fact, can be operated periodically on a scheduled on-time, off-time regimen. Typically, the patient can be at least temporarily independent of the device for periods of a few minutes to hours, since continuous pumping is not obligatory.
U.S. Pat. No. 6,471,633 discloses a dynamic aortic patch with an elongate membrane having a semi-rigid shell body portion and a relatively thin membrane portion defining an inflatable chamber. At least one passage extends through the shell body defining an opening in the inner surface of the shell body. The flexible membrane can be continuously bonded to the shell body adjacent the peripheral side edge to define the enclosed inflatable chamber in communication with the passage. The membrane optionally has a reduced waist portion defining a membrane tension zone adjacent to the opening of the passage into the chamber to prevent occluding the entrance while deflating the chamber. An outer layer can be bonded to the outer side of the wall portion of the aortic blood pump and cut with a freely projecting peripheral edge portion to provide a suture ring for suturing the aortic blood pump in place within an incision in the aorta.
The operational lifetime of an implanted pump is a source of constant concern. The constant movement of blood, movement of the vessel wall and the movement of the deflecting membrane relative to the pump shell, all impact pump operational lifetime. There is a continuing need for extending the number of inflation/deflation cycles a pump can support prior to failure so as to make a permanently implantable cardiac assist device a viable option for more heart patients.